Optical remote sensing of the Gulf of Gabès – relation between turbidity, Secchi depth and total suspended matter

Abstract. Optical remote sensing is used here in the Gulf of Gabès to provide scientific information to support environmental management. The Gulf of Gabès is located in the southern east coast of Tunisia. It is a shallow continental shelf with semi-diurnal tides with average amplitude of 2 m. Industrial activities in this area since the early 1970s may have contributed to the degradation of the biodiversity of the ecosystem with eutrophication problems, and disappearance of benthic and planktonic species. To assess the long-term effect of anthropogenic and natural discharges on the Gulf of Gabès, turbidity and light penetration in the coastal waters is assessed from in situ measurements of total suspended matter concentration (TSM), Secchi depth and turbidity (TU) and from remote sensing data using a semi empirical algorithm to retrieve turbidity and total suspended matter products from moderate resolution imaging spectrometer MODIS Level 2 (L2) data.